IDF: DTCP over IP

New-look content distribution

By Will Head | 18 September 03

DTCP-IP (digital transmission content protection over internet protocol) may not be snappy or easy to say, but it has huge implications for digital content distribution and how we'll use music and films in the future.

Announced at IDF (Intel Developer Forum), DTCP-IP extends a recognised secure digital distribution mechanism into the home network. It's no good having a digital home if there's no content to play on it, DTCP-IP provides a way for this to happen.

DTCP-IP offers a compromise between piracy concerns from content providers and ease of use for consumers. Without a system that satisfies both, the digital home will never become a reality.

One of the main criticisms of the supposed digital age we're living in is the lack of available legitimate content. Movie studios and record companies have been slow to embrace the digital era, citing lax copyright protection as the main reason. DTCP-IP means they now have no excuse not to join in. No more whining about file swappers, DTCP-IP provides a way for those that want to pay for digital content (and there's a fair few out there) to be able to buy it and use it with the ease of use of analogue content.

So, what exactly is DTCP-IP? According to Intel it's a link protection technology to supply digital content to co-located rendering devices. In English, that means it provides a secure digital link to output devices like TVs or speakers.

It's fairly easy to set up a secure system on a single computer, but if you want to keep all your content in one place and access it from any device then DRM (digital rights management) gets in the way. DTCP-IP allows content to stay secure on its way to the playback device.

The system works on the basis of trust. The server negotiates with the client and, once it establishes that it's a trusted device it can communicate with, it sends the data in encrypted form. Because server and client understand one another, the client can decrypt and display the data. As the system is entirely secure there's no need for draconian copy protection measures and users can go back to enjoying the ease of use provided by analogue systems.

The aim of DTCP-IP is to keep the content you've paid for inside the system you own, rather than locking it down to a single device at a time, which is the way current DRM systems work.

Analogue content is fairly easy to move around the various devices you have — like copying a CD on to tape to play in the car. While this technically violates copyright, it's an accepted practice providing you own the original CD. With DTCP-IP, transferring music to your car would simply be a matter of parking up in the garage and wirelessly downloading the tracks to your car player. As long as the server trusts that the player in the car belongs to you, no other enforcement is necessary.

As far as the consumer is concerned, providing you're only transferring content between devices you own, the system is completely transparent. When it comes to content producers, there are a couple of clever tricks to keep them happy.

Firstly ? and here comes the science ? DTCP-IP packets only have a TTL (time to live) of three. TTL is an online system used to ensure lost packets of data don't rattle round the internet forever. Each time a packet passes a router on its way to its destination, the router subtracts one from its TTL. When the TTL reaches zero the packet dies. Over the internet, the distance between you and your neighbour is generally at least six hops. A TTL of three means that transferring content over your own network is no problem; trying to lend it to someone else over the internet isn't so easy.

Secondly, the DTCP-IP spec allows for the licence of trusted devices to be revoked. So, for example, if a manufacturer produces a device that's easy to hack then it will lose its trusted status. Any DTCP-IP device created from that point onwards wouldn't be able communicate with the compromised device. There are also provisions within the spec to prevent content playing on compromised devices, although there are no current plans to implement it.

DTCP-IP provides a secure network environment, within which the content protects itself. To the user it's completely transparent, providing they don't try to move it off their own network, and for the content provider it offers a secure environment into which they can supply digital content with as much, if not more, protection than in the analogue realm.

It's a win-win situation that could prove this digital home idea really has something in it other than hype.